This invention relates to a pager receiver for use in carrying out unidirectional communication in a paging system.
A recent remarkable development of an integrated circuit technique makes a pager receiver compact or portable and multifunctional. Preferably, the pager receiver has a long life. Inasmuch as a battery is used as a power source in such a portable pager receiver, a life time of the portable pager receiver is dependent upon that of the battery. Therefore, electric power must not be wasted in the pager receiver. In other words, useless operation should strictly be restricted. For this purpose, a battery saving operation is carried out in such a portable pager receiver during nonreception of an address signal, namely, a call number signal destined for the portable pager receiver.
A wide variety of codes have been proposed for a conventional paging system. By way of example, the codes may be exemplified by the POCSAG code which is an abbreviation of The British Post Office Code Standardisation Advisory Group code and which has been published in "A standard code for radiopaging" by The British Post Office (July, 1979). The POCSAG code comprises a preamble and a plurality of batches following the preamble. Each batch lasts a predetermined duration and comprises a synchronization codeword and a plurality of frames equal in number to eight. A number of pager receivers are clustered into eight groups so as to carry out communication through the respective frames. Each frame is divided into two parts for address or message codewords. It should be noted here that a message is variable in length and may be long in comparison with the length of each codeword. Therefore, a plurality of codewords might be necessary for transmission of the message. In this event, not only a preassigned frame but also the following one or ones of the frames should be occupied by the pager receiver in question to transmit such a long message.
During transmission of the long message, the occupied frames can not be used by the other pager receivers. Nevertheless, by design, such other pager receivers well become operative each time that the predetermined period expires. Electric power is therefore wasted during such an invalid operation and is undesiredly consumed by the other pager receivers, even when the conventional battery saving operation is carried out.
In addition, new services and functions may be contemplated by the use of such a pager receiver.